Add temporary files repositories in integration tests

This is intended to catch problems with temporary files stored in the
backend, even if the responsible component forgets to test for those.

cmd/restic/cmd_init_integration_test.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"context"
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/restic/restic/internal/repository"
@@ -16,6 +18,11 @@ func testRunInit(t testing.TB, opts GlobalOptions) {
 
 	rtest.OK(t, runInit(context.TODO(), InitOptions{}, opts, nil))
 	t.Logf("repository initialized at %v", opts.Repo)
+
+	// create temporary junk files to verify that restic does not trip over them
+	for _, path := range []string{"index", "snapshots", "keys", "locks", filepath.Join("data", "00")} {
+		rtest.OK(t, os.WriteFile(filepath.Join(opts.Repo, path, "tmp12345"), []byte("junk file"), 0o600))
+	}
 }
 
 func TestInitCopyChunkerParams(t *testing.T) {